A fuel cell generates electric energy by causing a reaction between an oxidizing gas and a hydrogen gas serving as a fuel gas. A fuel cell system that is incorporated in an automobile or the like is controlled so as to convert chemical energy in hydrogen fed to the fuel cell (hereinafter called “hydrogen energy”) into electric energy at high efficiency (hereinafter referred to as “high-efficiency power generation”) during normal operations. Therefore, a fuel cell that performs high-efficiency power generation has a small proportion of conversion from the hydrogen energy to thermal energy, and shows a small quantity of heat generation.
As a consequence, a heat quantity necessary for warming up the fuel cell to a temperature suitable for electric power generation (in the vicinity of 80° C.) fails to be generated. Moreover, when the fuel cell system has a heating apparatus, the thermal energy produced from the fuel cell at the time of the high-efficiency power generation is small, and is insufficient for the heat source for heating. In view of this, a fuel cell system that aims at supplementing the deficient heat quantity has been under development.
A fuel cell that is caused to generate electric power at low efficiency by reducing the amount of air to be supplied is known as a conventional fuel cell system (for example, see Patent Document 1). This enables an increase in the heat generation quantity for warming up the fuel cell.
A conventional fuel cell system having a heating apparatus is provided with heating means for heating a cooling medium, and a heat exchanger for supplying the heat used for the heating for air-conditioning in a cooling medium circulation passage of the fuel cell, for the purpose of supplying a heat quantity necessary for heating (hereinafter referred to as a “heating heat quantity”) (see, for example, Patent Documents 2 and 3). In the case where the heat generation quantity from the fuel cell is small, the deficient heat quantity is supplied by heating the cooling medium by means of the heating means.
Patent Document 1: JP-A-2004-30979
Patent Document 2: JP-A-2004-311229
Patent Document 3: JP-A-2007-38952